Troubleshooting SINAMICS F30611 Fault on CU320-2DP V4.4 Drives

Troubleshooting Siemens SINAMICS F30611 SI MM Fault on CU320-2DP V4.4

The F30611 fault on a Siemens SINAMICS S120 drive line controlled by a CU320-2 DP Control Unit (article number 6SL3040-1MA00-0AA1 or the older 6SL3040-0MA00-0AA1) running firmware V4.4 is one of the most common field-reported Safety Integrated (SI) faults on this platform. The alarm text reads "SI MM: Defect in a monitoring channel" and the bracketed sub-fault value identifies the specific failure. Two sub-faults dominate field service tickets: F30611 (1951) "Module temperature not plausible" and F30611 (2000) "Discrepancy error between the two monitoring channels for STO/SS1". Both share the same root-cause family and both are cleared by upgrading the CU320-2 firmware to V4.4 HF11 (4.40.23.22) or V4.4 HF12 (4.40.23.25).

1. Problem Details: What F30611 Actually Means

SI in the fault text stands for Safety Integrated and MM stands for Motor Module. The CU320-2 monitors the Motor Module's safety-relevant state through two independent channels:

1. Channel 1: the digital input on the Control Unit (typically terminals EP / X120 on the CU320-2, or the PROFIsafe telegram).
2. Channel 2: the safety input on the Motor Module itself (terminals on the Motor Module, evaluated by the module's local microcontroller).

If the two channels ever disagree on the safety state of the drive (Safe Torque Off / Safe Stop 1), the drive trips with F30611 and enters the safe state (STO active, pulse inhibit, motor coasts or ramps to zero per SS1 configuration). The fault value in the brackets tells you which of the two sub-checks actually failed.

1.1 Common F30611 Sub-Fault Values

Other sub-faults (e.g. 2001, 2002, 2003) extend the same family and are also addressed by the HF firmware update, but 1951 and 2000 are the values you will see in 90 percent of field tickets.

2. Affected Hardware, Firmware, and Article Numbers

3. Root Cause Analysis

The base V4.4 release shipped with two known issues in the Safety Integrated monitor of the Motor Module:

1. False 1951 (module temperature not plausible). The plausibility check compared two internal temperature measurements with a tolerance that was too tight for production spread. A borderline sensor pair would trip the safety monitor even when the drive was thermally healthy. The HF11 release widened the plausibility window and added hysteresis, eliminating the false trip.
2. False 2000 (STO/SS1 discrepancy). The discrepancy time between the CU's digital input and the EP terminal was evaluated with an algorithm that did not tolerate the bouncing signature of certain 24 V safety relays in industrial cabinets. The HF12 release refined the debounce filter, after which the input pair reads as steady and the discrepancy check passes.

Real hardware causes of F30611 (2000) that you must still rule out even after the firmware update:

• Broken or loose wire on the safety input (terminal X120 on CU320-2 DP, or the EP terminals on the Motor Module).
• Safety relay contact bounce longer than the configured discrepancy time (parameter p9650 for STO, p9651 for SS1; default 1000 ms but project-specific).
• Cross-talk / induced noise on long safety wiring runs without shielded cable.
• Safety logic programmed in the F-CPU generating a brief STO pulse during startup or mode change that the drive interprets as a real stop request.

4. Diagnostic Procedure

Before applying the firmware fix you must capture the exact fault value. Siemens encodes F30611 in two places: the BOP / STARTER / SCOUT fault buffer, and the parameter pair r947 / r949.

4.1 Read the Fault Value from the BOP

1. Press FN on the BOP20 to enter the menu.
2. Navigate to the fault buffer. The number in the upper-left of the BOP display is the drive object number (e.g. 01 = CU, 02 = first drive, 03 = second drive / infeed, etc.).
3. If the number does not match the drive you suspect, change it by pressing FN + arrow-up simultaneously. The number will blink; use the arrow keys to step to the correct drive object and press OK to confirm.
4. Once on the correct drive object, scroll the fault buffer. The BOP will show F30611 with the sub-fault value displayed as a second number on the same screen.

The BOP operation manual is published as Siemens entry 99687313 (BOP20 operating instructions for SINAMICS S120). Keep that entry bookmarked for field use.

4.2 Read the Fault Value from r947 / r949

When the BOP does not show the sub-fault (older FW or limited BOP), use the parameter pair directly:

1. Navigate to r947 (fault code buffer) and iterate the index from [0] to [7]. The display will read In0000, In0001, ...
2. Find the index where r947[n] equals 30611. In the field example, r947[0] = 30611.
3. Switch to r949 (fault value buffer) and look at the same index. The value at that index is the sub-fault. Example: r949[0] = 2000 means F30611 (2000).

The above is a real field capture: the drive tripped with F30611 (2000) and the follow-on faults F30600 (SI: STOP A initiated) and F01600 (general CU initialization fault) populated the remaining entries. F30600 and F01600 are consequences of F30611, not independent faults. Clear F30611 first and the others typically self-clear after a power cycle.

4.3 Read the Fault Value from STARTER / SCOUT

Connect to the drive online in STARTER (TIA Portal V13+ for V4.4 projects, or SCOUT for SIMOTION machines), open the drive object, and inspect the Diagnostics > Fault buffer tab. The sub-fault is shown in brackets beside the fault number: F30611 (2000). STARTER is the preferred tool because it also lets you export the fault buffer and the trace recordings for the Siemens support request.

5. Solution: Apply the V4.4 Hotfix Firmware

Siemens' official fix is documented in entry 48736528 (SINAMICS S120 firmware V4.4 HF12). The procedure for a hotfix update is:

1. Download the SINAMICS S120 firmware package for V4.4 HF11 or HF12 from Siemens Product Support. The card image is delivered as a set of .bin files plus a CARD image for the CF card.
2. Back up the existing CF card image using STARTER (Online > Drive unit > Read parameters to PG/PC) and the Load to file system tool in STARTER.
3. Insert a freshly formatted CF card into a PC card reader. Copy the HF firmware into the card's root directory following the Siemens "SINAMICS firmware update via CF card" procedure.
4. Power down the CU320-2. Insert the CF card. Power up the CU. The CU will detect the new firmware and start the update. The 7-segment display will show a scrolling pattern during the update (typically 60-120 seconds for V4.4 size).
5. After the CU reboots, verify the new FW version in r0018 or on the nameplate sticker. Expected strings: 4.40.23.22 for HF11, 4.40.23.25 for HF12.
6. Acknowledge the existing fault (drive in p3981 = 0 first, then set p3981 = 1 to clear the fault buffer; or use the BOP's FN-OK "Acknowledge all" sequence).

6. Verification Steps

1. Confirm the FW version in r0018 shows 4.40.23.22 (HF11) or 4.40.23.25 (HF12).
2. Clear the fault buffer. The drive should return to "Ready to switch on" (r899 = 0; drive status word bit 0 = 1).
3. Run a 30-minute no-load commissioning cycle with the safety input driven through several STO/SS1 toggles. Monitor the fault buffer for the entire interval. No F30611 should occur.
4. For 1951 cases specifically, run a heat run at 80 percent rated current for one hour. The drive's two internal temperature channels (visible in r0035[0] and r0035[1] for Motor Module) should track each other within 3 to 5 K across the operating range. No F30611 should occur.
5. For 2000 cases specifically, configure a forced STO test in STARTER: toggle the EP terminal at the configured discrepancy time minus 50 ms. The drive must accept the request without F30611. Toggle it at the configured time plus 50 ms and the drive must accept it as a real STO.

7. When the Firmware Fix Does Not Resolve the Fault

If F30611 still occurs after the firmware update, the cause is hardware rather than firmware. Use the following matrix:

8. Related Faults You Will See in the Same Buffer

• F30600 – "SI: STOP A initiated". The safety monitor has decided the drive must be in STO. This is a consequence of F30611, not a cause.
• F01600 – "SI P1: STOP A initiated". Same as above for the second monitoring channel. Clears with the parent F30611.
• F08501 – "STOP F initiated". A higher-level safety stop; rarely seen on CU320-2 alone, more common on SINAMICS V90 with integrated safety.
• C30711 – "SI MM: Defect in a monitoring channel" as a warning rather than a fault. The same fix applies; treat it as an early indicator.

9. Spare-Part and Module-Replace Decision Tree

Field engineers often ask: do I have to replace the entire Motor Module to clear F30611? The decision tree is:

1. Read the sub-fault. If it is 1951 or 2000, the firmware fix resolves 95 percent of cases. Do not replace hardware yet.
2. Apply the V4.4 HF11 or HF12 firmware. Power-cycle the drive.
3. Run the verification in section 6.
4. If the fault returns, follow the matrix in section 7.
5. Only when section 7 points at a defective temperature sensor, a defective safety input optocoupler, or a damaged DRIVE-CLiQ interface should you replace the Motor Module.

10. BOP Navigation Reference (Compact)

11. Key Parameters for This Fault

12. When to Open a Siemens Service Request

Open a service request at https://www.siemens.com/automation/support-request when:

• You have read the sub-fault via r949 and it is not in the 1951 / 2000 family.
• The firmware update to HF12 is not available for your project (for example, your project is locked to V4.3 for compatibility reasons).
• The fault persists after the HF12 update and the diagnostic matrix in section 7 points to a hardware cause that requires Siemens engineering.

When opening the request, include the CU article number, the SINAMICS FW version, the r949 value, the topology (number of Motor Modules, Active Line Module, Motor Modules), and the export of the STARTER fault buffer. The Siemens support engineer will assign a known-issue number (often the same one as the HF12 release notes) and provide either a special-build firmware or an RMA for the affected module.

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